I was only negative $40 and it'd cost them more to take further action then to do anything, but what they did was kept emailing me saying if I don't fix it they'll go to collection agency.
I didn't do anything, they went to collection agency. I didn't do anything, then a few weeks later (after the date) paypal emailed saying I paid it off even though I did absolutely nothing.
But for your friend, $4k is obviously so far away from $40, so if it's real info they'll actually do something.